The 6V6 family of beam tetrodes came in many constructions and were very popular as the final audio stage of broadcast receivers. We have the original American metal valve 6V6 produced in the mid 1930s and subsequently used for military designs and a miniature glass tubular version the 6V6GT. The 6V6 shown here is of the large glass type and the inside of the envelope has a grey smoked finish.
The valves were capable of push pull use but the normal environment was as a single end output stage.
The pinch side on. Note the missing spigot - it has been broken off.
The envelope is effective in preventing a view of the electrodes. The cathode and screen grid can just be seen as can the anode shape with the seam in the centre of the working face.
The classic envelope is 44 mm in diameter, and excluding the IO base pins is 111 mm tall.
References: Datasheet, 1040 & 1043. Type 6V6G was first introduced in 1937.